1. Field of the Invention
The present invention relates to improvements in an empty bag supply method and empty bag supply apparatus in which an uppermost bag of a group of bags stacked in a conveyor magazine is sequentially taken out and transported along a predetermined bag transportation path, so that the bag is finally transferred to, for instance, a gripper of a bag packaging apparatus.
2. Description of the Related Art
Japanese Utility Model Registration No. 2603966 discloses a conveyor magazine; and in this conveyer magazine, a belt conveyor conveys a group of empty bags stacked in such a format that the bag mouths are facing forward and the upper bags shifted forward, and a fast-feed belt separates the uppermost empty bag from the group of empty bags on the belt conveyor and feeds it out forward. A toothed wheel is provided on the belt conveyor at the forward side of the fast-feed belt so that it feeds out forward the empty bag separated by the fast-feed belt, and further a positioning stopper is provided so that the tip end of the bag mouth of the empty bag fed by the toothed wheel comes into contact with it and the bag is thus positioned by this positioning stopper by the bag mouth. The empty bag positioned by the stopper in the conveyor magazine is changed from a roughly horizontal attitude to a substantially vertical attitude with the bag mouth facing upward and then supplied to a neighboring bag packaging apparatus.
In this type of a conveyor magazine-style bag supply apparatus, when supplying zipper-equipped bags or spout-equipped bags, problems would occur. More specifically, when an empty bag that is equipped with additional elements (for instance, a zipper, a spout or the like) that has certain thickness near the bag mouth is supplied, though an empty bag below the uppermost empty bag (next lower empty bags) is fast-fed by the fast-feed belt, the next empty bag may be impeded from being fed forward beyond the toothed wheel. This is because when the toothed wheel descends and contacts the uppermost empty bag, pressure is applied to the next lower empty bag through the uppermost empty bag, and as a result, the zipper, spout or other part of the next lower empty bag is caught on the toothed wheel, so that the forward movement of the bag is impeded. When this occurs, the next lower empty bag bends upward; and though the bag eventually returns to its original flat state when the toothed wheel ascends and the toothed wheel pressure is released, the bending and returning phenomenon can create irregular fetches and inappropriate positioning of the uppermost empty bag.
In the conveyor magazines disclosed in Japanese Patent Application Laid-Open (Kokai) Nos. 2006-123910 and 2006-143264, a bag is transported with its bottom facing in the bag feeding direction, so that the tip end of the bag bottom comes into contact with a stopper and the empty bag is thus positioned by the stopper (positioning by the bag bottom). Though this would resolve the above-described problem that would occur when positioning is made by the bag mouth as seen in Japanese Utility Model Registration No. 2603966 (in which next lower empty bags bend and return, creating inappropriate fetch or inappropriate positioning of the uppermost empty bag), it creates new problems as noted below even when the bag bottom faces in the bag feeding direction, since ultimately the empty bag must be supplied to the gripper of a bag packaging apparatus with the bag mouth facing upward.
(1) Because the empty bag is positioned by the bag bottom, whenever the bag surface of the empty bag is distorted in a wave shape in the direction of the length, the position of the bag mouth of the empty bag will not be consistent. As a result, in Japanese Patent Application Laid-Open (Kokai) No. 2006-123910, the suction position of a vacuum cup 17 tends to shift in the direction of the length of the empty bag, and in Japanese Patent Application Laid-Open (Kokai) No. 2006-143264, the gripping position of the gripping claw 41 will shift in the direction of the length of the empty bag; as a result, the empty bag's height (height position of bag mouth) when the empty bag is transferred to the bag packaging apparatus gripper will not be adequate. This creates a problem that the gripping position of the gripper becomes different in the direction of length for each empty bag.
(2) When empty bags supplied to the bag packaging apparatus are changed to those which are of different length dimensions, stopper adjustment is not required when positioning of the bag is made by the bag mouth as in Japanese Utility Model Registration No. 2603966; however, in Japanese Patent Application Laid-Open (Kokai) No. 2006-123910, the location of the stopper (12) needs to be changed; and in Japanese Patent Application Laid-Open (Kokai) No. 2006-143264, the location of the stopper (32) needs to be changed. Since the adjustment precision of the stoppers directly affects the precision of where the empty bag is supplied to grippers, adjustment work must be made extremely carefully, and thus it creates a major burden on the operator.